5052 aluminium for sheet metal parts: grade, thickness and formability

A 1.5 mm 5052 bracket bends cleanly at a 2 mm inside radius in H32 and splits at the second bend in H34. The alloy is identical on both drawings; the temper is not. When a buyer reports that "5052 aluminium is cracking", the answer is almost always a temper, a grain direction or a bend relief that was decided at quotation and never written on the print.

5052 aluminium is the 2.5% magnesium sheet alloy that most formed aluminium parts should use. It is not heat treatable, so every megapascal it holds comes from cold rolling, and every forming and welding operation gives some of it back. That single fact drives the grade, the temper, the radius and the weld design.

This page sets out the numbers a design engineer needs before releasing a 5052 part: what the H-temper suffix commits the mill to, which thicknesses a sheet metal shop can actually cut and form, how radius and springback behave at a modulus one third of steel, and what a weld does to the parent metal. The corrosion and coating side is covered in 5052 aluminium corrosion and finish compatibility.

What 5052 aluminium is, and what the H-temper changes

5052 is an aluminium-magnesium alloy with 2.5% magnesium and 0.25% chromium, and it cannot be strengthened by heat treatment. 6061 gains its strength from a solution-and-age cycle; 5052 gains strength only by being rolled cold. Anneal it — with a torch, a weld or a furnace — and it goes back to the O condition.

The temper suffix carries the strength guarantee. In H32 the 3 means strain-hardened and stabilised and the 2 means quarter-hard. H34 is stabilised half-hard, H38 stabilised full-hard, and O is annealed. ASTM B209 sets the mechanical property limits for each temper and thickness range, so the mill certificate is a statement about tensile and yield, not about how the sheet will bend.

The stabilising digit is worth understanding. H24 is strain-hardened to half-hard and not stabilised, so the sheet continues to age at room temperature and can arrive harder than the last delivery. H32 and H34 are stabilised, which is why they are the tempers that belong on a drawing released for a two-year programme.

The design consequence is blunt. A part that is formed after cutting goes into H32 unless the drawing radius is generous enough for H34. A flat part that is only blanked and pierced — a louvre blade, a blanking plate, a hemmed cover — can use H38 and get 215 MPa yield for the same weight. A deep-drawn part needs O and finishes at 90 MPa, whatever the drawing calls out. If the strength requirement cannot survive that, 5052 is the wrong alloy and the decision belongs in when 5052 aluminium is the wrong material.

Which thickness of 5052 aluminium a sheet metal shop can hold

Stock sheet runs 0.5 mm to 6.0 mm. Above 6 mm the same alloy is supplied as plate, and plate is a different production route: cut, drilled, machined and bolted rather than cut, formed and welded. Ganesh cuts 0.8–20 mm on the 12 kW fibre laser and forms up to 10 mm on the 200 T brake, so a 5052 part between 0.8 mm and 10 mm can be cut, formed, welded and powder coated without changing supplier.

Weight per unit area is thickness × 2.68 kg/m² per mm. That arithmetic decides more specifications than buyers expect:

A canopy door or a lift car panel in 1.5 mm 5052 saves 15.5 kg against the same panel in CRCA, and the saving is closer to 20.7 kg at 2.0 mm. On an eight-panel door set that is 124 kg off the moving mass. That is the argument for the material; the counter-argument is stiffness, because the modulus is 70.3 GPa against 205 GPa for steel, so the aluminium panel deflects about three times as far at the same thickness. If the drawing needs the steel panel's stiffness, the aluminium panel has to be thicker, and the weight saving narrows or disappears. Run that check before the material is approved.

Thickness tolerance is the other half of the thickness decision, and it moves blank size, weight and welded stack-up. It has its own page: thickness tolerance and its effect on 5052 aluminium parts.

5052 aluminium formability: radius, grain and springback

The radius comes from the temper, not the alloy name

For a 90° bend, 5052-H32 forms at an inside radius of 1.0–1.5 × thickness. H34 needs 1.5–2.0 × and H38 needs 3 × or more. O temper goes to about 0.5 ×. Those figures are empirical limits built from trials, not from the elongation on the certificate, and the minimum bend radius table by material explains why the two numbers disagree.

Grain direction is the second variable and it is invisible on most drawings. The rolling direction runs along the length of the sheet. A bend line perpendicular to it bends across the grain, which is the strong direction for forming; a bend line parallel to it bends with the grain and needs one temper step softer or about 0.5 × thickness more radius. Leave a note on the drawing — "critical bends across grain" — and let the nesting engineer orient the part, because a 2,500 × 1,250 mm sheet only offers one orientation.

Hole and slot placement near a bend is the third. A hole closer to the bend line than the bend allowance plus half the hole diameter distorts into an oval. The rule and its derivation are in hole-to-bend distance in sheet metal design.

Springback is the number that changes the brake programme

Springback scales with yield strength divided by modulus, and with the radius-to-thickness ratio. 5052-H32 gives 160 ÷ 70,300 = 2.28 × 10⁻³; CRCA at 250 MPa gives 1.22 × 10⁻³. At the same radius-to-thickness ratio a 5052 bend springs back about 1.9 times as far as a CRCA bend, which on a 90° bend at R = 1.5t means 3–5° in H32 against 1.5–2° in CRCA. H34 pushes that to 4–6°, and H38 to 6–8°.

The brake compensates by overbending, and the Delem control holds the correction in the program. The trap is a part transferred from steel: the tooling, the die opening and the programmed angle all carry over, the first-off comes out 4° open, and someone blames the material.

Tonnage is not the constraint on aluminium. Air-bending force per metre is 1.42 σu t² / V in kN/m, where σu is tensile strength in MPa, t is thickness in mm and V is the die opening in mm. For 2.0 mm 5052-H32 at 215 MPa with a 16 mm V die: 1.42 × 215 × 4 ÷ 16 = 76 kN/m. The same calculation for 2.0 mm CRCA at 450 MPa gives 160 kN/m. A 200 T brake across a 4,450 mm bed is good for about 440 kN/m, so 5052 is never tonnage-limited on that machine; the limits are the punch tip radius, the die opening and the springback correction.

Blank size: a worked bend allowance

Take a 2.0 mm 5052-H32 bracket with a 90° bend, a 2.0 mm inside radius (1 × t) and flange lengths of 40 mm and 30 mm. With K = 0.44:

• Bend allowance = (π/180) × 90 × (2.0 + 0.44 × 2.0) = 1.5708 × 2.88 = 4.52 mm.
• Outside setback = (2.0 + 2.0) × tan 45° = 4.00 mm.
• Bend deduction = 2 × 4.00 − 4.52 = 3.48 mm.
• Flat length = 40 + 30 − 3.48 = 66.52 mm.

Now suppose the first article measures 66.90 mm flat. Solve back: bend allowance = 66.90 − 62.00 = 4.90 mm, so 4.90 ÷ 1.5708 = 3.12 mm, and K = (3.12 − 2.0) ÷ 4.0 = 0.56. The K-factor was not 0.44 for that tool and that radius. Issue a corrected flat pattern before the nesting run, not after, because the difference of 0.38 mm per bend multiplies through a folded box. The mechanics of K are in k-factor in sheet metal bending.

Welding 5052 without losing the temper

5052 welds cleanly with MIG or TIG and 5356 filler. 5356 carries 5% magnesium, matches the parent alloy, gives a stronger joint than 4043 and anodises to a closer colour, which matters on a visible aluminium frame. 4043 is fine for non-structural joints and is more forgiving on dirty edges.

The heat-affected zone is the design issue. Welding takes the parent metal beside the bead back towards O temper, so a joint in 5052-H32 should be designed at about 110–130 MPa rather than the parent 160 MPa. There is no post-weld ageing treatment that restores it, because the strength was put in by cold rolling and cannot be put back in a finished part. If the joint has to carry full parent stress, thicken the section locally at the weld or move the weld to a lower-stress location.

Two physical properties drive the rest. Thermal conductivity of 138 W/m·K is nearly three times that of mild steel, so heat leaves the weld pool and the surrounding panel stays hot; thermal expansion of 23.8 µm/m·K is double steel, so the contraction on cooling is double. The result is bow and shrink, and the sequence and fixture that control it are set out in welding aluminium sheet assemblies.

5052 aluminium on the Ganesh route

5052 parts are cut on the 12 kW fibre laser with the 40 ft × 16 ft bed, which takes full-length canopy sides and rack rails without a splice, and formed on the 200 T 5-axis CNC press brake with its 4,450 mm bed to 10 mm. Welded frames run through three CLOOS robotic MIG cells or the 30-plus manual MIG, spot and SPM stations, with fixtures designed in our own tool room, then through seven-tank pretreatment and the 18 ft × 14 ft powder booth.

Typical sheet metal tolerance is ±0.5 mm, tighter on critical features by agreement, and both plants hold ISO 9001:2015 and ISO 14001:2015. The same lines cut and form copper, brass and aluminium for electrical and non-ferrous work, described on the copper, brass and aluminium fabrication page. Every 5052 part in the custom parts range is quoted with its temper and grain direction stated, because those two fields decide whether the part can be made at the price quoted. The materials and grades hub collects the rest of the grade-selection work, from the corrosion and finish behaviour of 5052 to the thickness band that moves the flat pattern.

What to put on the drawing

1. Alloy and temper by designation — "5052-H32", never "aluminium" or "Al 2.5 Mg".
2. Thickness with its tolerance, or a reference to the mill standard you want.
3. Inside bend radius for every bend, and which bends are critical.
4. Grain direction requirement, if the part has a tight bend or a visible face.
5. Flat pattern basis: whether you supply the flat or expect the supplier to develop it from the K-factor.
6. Weld symbol, filler alloy and the acceptance level for the joint.
7. Finish and the faces to be finished, including any anodised or bare surfaces.
8. Flatness and twist limits on the formed part, in millimetres over the part length.

Ordinary dimensional tolerances default to ISO 2768-1 when the drawing does not call out individual tolerances, which covers linear and angular dimensions but says nothing about bend angle or flatness. Those need their own notes.

When 5052 aluminium is the wrong choice

5052 stops being the right answer in four situations. Above about 200 MPa yield the alloy runs out of strength, and 6061-T6 or 6082-T6 at 276 MPa, or a steel part, is the correct selection. Sustained service above roughly 150 °C softens the alloy, and there is no temper to fall back on. Surfaces that see sliding abrasion — a chute liner, a fork entry point — wear through a 5052 panel quickly, and steel or a hard-anodised part is the honest choice. And where the design is stiffness-driven rather than strength-driven, aluminium needs 2.9 times the thickness of steel for the same deflection, which usually erases the weight advantage.

We cut and form 5052 from 0.8 mm to 10 mm formed, and we will say so when the drawing asks for something outside that. Send the revision with the temper, radii and quantity through request a quote, and the quotation will state the flat pattern basis and the weld filler it assumes.